Octopus by Yena Yoo

Octopi are a group of cephalopods. The common octopus is found in the tropical and temperate waters of the world’s oceans. They can grow to about 4.3 feet (1.3 meters) in length and weigh up to 22 lb (10 kg), although averages are much smaller. They prey on crayfish, and mollusks, and will sometimes use their ink to disorient their victims before attacking. They are also known for their intelligence. [1]

Octopi use a pair of well developed gills along with well developed blood vessels.

They use a mantle. An octopus's mantle is a muscular structure that contains all of its organs, including gills, hearts, a digestive system and reproductive glads. It is located behind its head and across from its arms. It is The mantle's strong muscle assist with respiration and help protect sensitive organs.

Octopi also respire through their epidermis, the outer layer of skin.

Lastly With the siphon, they pump water through the gill system to enable them to breathe. (Note, The siphon is also used for movement as the octopus pumps his/her way through the water rather than swimming. )[5,6]